Add community text submissions, and make custom text usable for study

Submissions
- POST /api/texts proposes a passage; nothing reaches players until a
  moderator approves it. GET /api/texts serves the approved set, which the
  client merges on top of its bundled packs at startup.
- Validation the server enforces rather than trusts: category from a fixed
  list, 40 to 600 characters, no control characters (a newline makes a
  passage untypeable in a single-line input), attribution length, and a
  unique index on md5(lower(btrim(content))) so the same passage cannot be
  submitted twice under different whitespace or casing.
- Moderation is a flag on users. The queue and the review endpoint both
  refuse a non-moderator, and reviewing an already-reviewed submission is a
  404 rather than a silent second write.
- Submissions are rate limited per user: enough for a real contributor, not
  enough to fill the queue from a script.
- A Contribute screen carries the form, your own submissions with their
  status, and - for moderators only - the review queue.

This is the half of TypeRacer's model the packs could not reach by authoring:
their corpus is roughly twelve thousand passages, grown by submission.

Custom text as a study tool
- Imported documents are kept between visits, with how far through each one
  you are. Custom text lived only in memory, so importing a set of notes and
  reloading the page lost them - fine for pasting a paragraph to race,
  useless for working through a file over several sittings.
- Position is recorded when a segment is finished, not when the next is
  started, so closing the tab after a segment does not lose it.
- Markdown is chunked as markdown: fenced code blocks are kept whole and
  typed line by line, and the decoration - hashes, asterisks, backticks,
  link brackets, table pipes - is stripped so what you retype is the
  material rather than the punctuation around it.
- Everything stays on the device. Notes are not uploaded anywhere.

Fixed while doing it: a chunk could contain a newline, which cannot be typed
in a single-line input at all. Any paragraph with a line break inside it --
ordinary in notes and in wrapped prose - produced an unfinishable segment.
Whitespace inside a chunk is now flattened.

1 files changed, 28 insertions, 0 deletions

diff --git a/crates/server/migrations/0010_text_submissions.sql b/crates/server/migrations/0010_text_submissions.sql
new file mode 100644
index 0000000..b735a8f
--- /dev/null
+++ b/crates/server/migrations/0010_text_submissions.sql
@@ -0,0 +1,28 @@
+- Community-submitted passages, the way a text corpus actually grows past
+- what fits in a repository. Nothing here reaches players until a moderator
+- approves it.
+ALTER TABLE users ADD COLUMN is_moderator BOOLEAN NOT NULL DEFAULT FALSE;
+
+CREATE TABLE text_submissions (
+    id TEXT PRIMARY KEY,
+    user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    category TEXT NOT NULL,
+    content TEXT NOT NULL,
+    attribution TEXT,
+    - Syntax language for code passages; NULL for prose.
+    language TEXT,
+    status TEXT NOT NULL DEFAULT 'pending' CHECK (status IN ('pending', 'approved', 'rejected')),
+    reject_reason TEXT,
+    reviewed_by TEXT REFERENCES users(id) ON DELETE SET NULL,
+    reviewed_at TEXT,
+    created_at TEXT NOT NULL
+);
+
+CREATE INDEX idx_text_submissions_status ON text_submissions(status);
+CREATE INDEX idx_text_submissions_user ON text_submissions(user_id);
+
+- One submission per passage, regardless of whitespace or case. Built on
+- md5() rather than a stored hash column so the constraint cannot drift out
+- of step with the content it is derived from.
+CREATE UNIQUE INDEX idx_text_submissions_dedupe
+    ON text_submissions (md5(lower(btrim(content))));