feat(search): tag-based page search surface + per-page tags & collections

Add the /search surface (Pages / Chapters / Mangas tabs) backed by
per-user page tags and per-page collections: schema (migration 0023),
backend endpoints for page tags/collections and tagged-page aggregations
(with the OCR text-search param reserved at 501), plus the frontend API
clients, library Page-tags tab, collection page sections, page context
menu / AddTagsSheet, and reader long-press wiring. Includes the
continuous-reader navigation fixes (?page=N handling, chapter-reset
timing, back-button pops history) and tag-normalization hardening
accumulated on the branch.

Bump version 0.60.2 -> 0.62.0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/migrations/0023_page_collections_and_tags.sql

@@ -0,0 +1,48 @@
+-- Per-page collections and tags. Collections become heterogeneous: the
+-- existing `collection_mangas` join holds whole mangas, this new
+-- `collection_pages` join holds individual pages. A page tagged or
+-- collected references the stable `pages.id` UUID, so re-uploading a
+-- chapter (which deletes and recreates the page rows) silently drops
+-- any saves attached to it — cascade is intentional, matching the
+-- semantics of the cover-image references in existing collections.
+
+CREATE TABLE collection_pages (
+    collection_id uuid NOT NULL REFERENCES collections(id) ON DELETE CASCADE,
+    page_id       uuid NOT NULL REFERENCES pages(id)       ON DELETE CASCADE,
+    added_at      timestamptz NOT NULL DEFAULT now(),
+    PRIMARY KEY (collection_id, page_id)
+);
+
+-- Reverse lookup: "which of my collections contain this page?" — the
+-- reader's context menu pre-checks the matching collection rows on
+-- open.
+CREATE INDEX collection_pages_page_idx ON collection_pages (page_id);
+
+-- Per-user, per-page free-form tags. Distinct from the manga-level
+-- shared `tags` taxonomy — these are personal annotations. Length cap
+-- 64 leaves room for `namespace:value` conventions (e.g.
+-- `character:askeladd`) without making the schema enforce them.
+CREATE TABLE page_tags (
+    id         uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id    uuid NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    page_id    uuid NOT NULL REFERENCES pages(id) ON DELETE CASCADE,
+    tag        text NOT NULL,
+    created_at timestamptz NOT NULL DEFAULT now(),
+    CONSTRAINT page_tags_tag_nonempty CHECK (length(tag) > 0 AND length(tag) <= 64)
+);
+
+-- One row per (user, page, tag). The repo upserts via ON CONFLICT DO
+-- NOTHING so re-tagging is a no-op (handler returns 200 instead of 201).
+CREATE UNIQUE INDEX page_tags_user_page_tag_uniq
+    ON page_tags (user_id, page_id, tag);
+
+-- "Show me everything I've tagged" — newest-first. Drives the library
+-- Page-tags tab.
+CREATE INDEX page_tags_user_idx ON page_tags (user_id, created_at DESC);
+
+-- "Show me what I've tagged X" — same tab, when a chip filter is
+-- active.
+CREATE INDEX page_tags_user_tag_idx ON page_tags (user_id, tag, created_at DESC);
+
+-- Per-page lookup for the context menu's contextual line.
+CREATE INDEX page_tags_page_idx ON page_tags (page_id);