docs(database): correct the Dashboard table creation steps (#50023)

Part 3 of a 5-PR stack on
`apps/docs/content/guides/database/tables.mdx`. Builds on #50022.

## Problem

Three claims fail the test that a reader following the page would hit a
wrong outcome.

**The Dashboard steps don't match the product.** They said to click
**New Table**, save, then click **New Column**. Columns are defined
inside the table creation panel, so a reader who follows the steps saves
a table with no columns and then hunts for a button that isn't part of
that flow. The labels are also sentence case in the product: **New
table** and **New column**.

**The Dashboard example diverges from the rest of the page.** The steps
created a table named `todos` with a `task` column, while the SQL tab
beside them and every later example use `movies`. A reader who took the
Dashboard path and then ran the first Loading data snippet got `relation
"movies" does not exist`.

**The page's SQL doesn't compose.** Running every fence in document
order showed that the many-to-many example under "Joining tables with
foreign keys" opened by creating `movies` again. A reader who already
created it got `relation "movies" already exists`, the block stopped, so
`actors` was never created, and the `private.salaries` example two
sections later then failed with `relation "public.actors" does not
exist`. **One redundant statement broke two sections.**

**The bulk loading example couldn't work.** `COPY` accepts text, CSV,
and binary input, and the page listed JSON. `\COPY movies FROM
'./movies.csv'` expects a value for every column, and `movies` has three
while the sample file has two. The options example passed `CSV HEADER`
against a file with no header row, which silently dropped the first
record. Found by CodeRabbit.

## Solution

Rewrites the five Dashboard steps to match the panel and to produce
`movies`, so both tabs leave the reader in the same place. Drops the
redundant `create table movies` from the many-to-many block; the prose
above it already says "You have a list of `movies`". Names the columns
in both `COPY` commands, corrects the format list, points the `HEADER`
example at a file that has one, and removes the space before each quoted
CSV field.

Dashboard changes verified against `TableEditor.tsx`, which renders
`ColumnManagement` inside the creation panel; `TableEditorMenu.tsx` and
`ColumnList.tsx` for the labels; and `DEFAULT_COLUMNS` in
`TableEditor.constants.ts` for the `id` and `created_at` columns the
editor adds.

## Checked and deliberately left

- `grant all on table transcripts to authenticated`. Broader than the
example needs, but a reader gets the working result the page promises,
so it doesn't meet the bar for this branch.
- "By default, views are accessed with their creator's permission."
Accurate. `security_invoker` is opt-in.
- `salary bigint` in the private schema example. Left here; it changes
in #50025, where the page starts recommending `numeric` for money and
the example becomes inconsistent with it.

## Flagged, not changed

- The `api-create-table-sm.mp4` video in the Dashboard tab may show the
older flow. Its contents weren't verified.
- **Nothing in the Views section is runnable.** All nine of its fences
depend on `students`, `courses`, and `grades`, which the page shows as
rendered tables and never creates. Supplying that DDL is new content, so
it isn't this branch's job, but it's worth a ticket.

## Manual testing

Preview:
https://docs-git-docs-tables-technical-supabase.vercel.app/docs/guides/database/tables

1. Open the preview and read the Dashboard tab under "Creating tables".
It says **New table**, creates `movies`, and defines both columns in the
same panel.
2. Open the Table Editor in a project and click **New table**. The panel
has a **Name** field and a **Columns** section, and there is no separate
**New Column** step.
3. In a fresh local database, run the SQL fences from "Creating tables"
through `private.salaries` in page order. Each one succeeds.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **Documentation**
- Updated the “Creating tables” guide to use a `movies` table with
`name` and `description` columns.
- Reworded and consolidated the table-creation steps, including the
`created_at` column in the SQL example.
- Updated bulk data loading instructions for CSV imports, connection
setup, named columns, and header-delimited files; removed JSON from the
listed formats.
- Simplified the many-to-many example by removing the redundant `movies`
table definition.
  - Clarified schema selection based on the current `search_path`.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/docs/content/guides/database/tables.mdx

@@ -76,9 +76,9 @@ and run the SQL queries yourself.
 </video>
 
 1. Go to the [Table Editor](/dashboard/project/_/editor) page in the Dashboard.
-2. Click **New Table** and create a table with the name `todos`.
-3. Click **Save**.
-4. Click **New Column** and create a column with the name `task` and type `text`.
+2. Click **New table**.
+3. Enter `movies` in the **Name** field.
+4. Under **Columns**, click **Add column** and enter `name` with type `text`, then add `description` with type `text`. Leave the `id` and `created_at` columns as the editor created them.
 5. Click **Save**.
 
 </TabPanel>
@@ -88,7 +88,8 @@ and run the SQL queries yourself.
 create table movies (
   id bigint generated by default as identity primary key,
   name text,
-  description text
+  description text,
+  created_at timestamptz default now()
 );
 ```
 
@@ -276,27 +277,27 @@ await supabase.From<Movie>().Insert(movies);
 #### Bulk data loading
 
 When inserting large data sets, use Postgres's [COPY](https://www.postgresql.org/docs/current/sql-copy.html) command.
-This loads data directly from a file into a table. Several file formats are available for copying data, including text, CSV, binary, and JSON.
+This loads data directly from a file into a table. `COPY` accepts text, CSV, and binary input.
 
 For example, to load a CSV file into your `movies` table:
 
 ```text ./movies.csv
-"The Empire Strikes Back", "After the Rebels are brutally overpowered by the Empire on the ice planet Hoth, Luke Skywalker begins Jedi training with Yoda."
-"Return of the Jedi", "After a daring mission to rescue Han Solo from Jabba the Hutt, the Rebels dispatch to Endor to destroy the second Death Star."
+"The Empire Strikes Back","After the Rebels are brutally overpowered by the Empire on the ice planet Hoth, Luke Skywalker begins Jedi training with Yoda."
+"Return of the Jedi","After a daring mission to rescue Han Solo from Jabba the Hutt, the Rebels dispatch to Endor to destroy the second Death Star."
 ```
 
-[Connect](/docs/guides/database/connecting-to-postgres#direct-connection) to your database directly and load the file with the `COPY` command:
+Set `DATABASE_URL` to your [direct connection string](/docs/guides/database/connecting-to-postgres#direct-connection), then load the file with the `COPY` command. Name the columns the file contains, so Postgres doesn't expect a value for `id`:
 
 ```bash
-psql -h DATABASE_URL -p 5432 -d postgres -U postgres \
-  -c "\COPY movies FROM './movies.csv';"
+psql "$DATABASE_URL" \
+  -c "\COPY movies (name, description) FROM './movies.csv' WITH (FORMAT csv);"
 ```
 
-You can also use the `DELIMITER`, `HEADER`, and `FORMAT` options as defined in the Postgres [COPY](https://www.postgresql.org/docs/current/sql-copy.html) docs.
+You can also pass options such as `DELIMITER` and `HEADER`, as defined in the Postgres [COPY](https://www.postgresql.org/docs/current/sql-copy.html) docs. `HEADER` skips the first line of the file, so use it only when that line names the columns:
 
 ```bash
-psql -h DATABASE_URL -p 5432 -d postgres -U postgres \
-  -c "\COPY movies FROM './movies.csv' WITH DELIMITER ',' CSV HEADER"
+psql "$DATABASE_URL" \
+  -c "\COPY movies (name, description) FROM './movies-with-header.csv' WITH (FORMAT csv, HEADER, DELIMITER ';');"
 ```
 
 If you receive an error `FATAL:  password authentication failed for user "postgres"`, reset your database password in **Database Settings** and try again.
@@ -326,12 +327,6 @@ For example, consider this situation:
 - An `actor` can perform in several movies.
 
 ```sql
-create table movies (
-  id bigint generated by default as identity primary key,
-  name text,
-  description text
-);
-
 create table actors (
   id bigint generated by default as identity primary key,
   name text
@@ -411,7 +406,7 @@ width={1600}
 height={1145}
 />
 
-If you don't explicitly pass a schema when creating a table, Postgres creates the table in the `public` schema.
+If you don't explicitly pass a schema when creating a table, Postgres creates the table in the first schema in the current [`search_path`](https://www.postgresql.org/docs/current/ddl-schemas.html#DDL-SCHEMAS-PATH). The default path is `"$user", public`, so on a new project that's the `public` schema.
 
 You can create schemas to organize tables. For example, you might want a private schema that's hidden from your API: