Initial commit: The Daily EPUB full implementation

Full implementation of a personalized daily newspaper delivered as an
EPUB.

Articles are pulled from a local self-hosted Miniflux instance, enriched
with comments, summarized and filtered by DeepSeek AI, and then
assembled into two EPUB editions: standard and optimized for the Xteink
X4 e-ink reader. Both are served by the local self-hosted BookOrbit OPDS
server in a separate library. Then the X4 edition is futher converted to
XTC format and served over a separate OPDS server hosted by the Rust
binary. Runs are tracked in a local SQLite database so runs are
idempotent per date.

Full documentation of the plan is in docs/plans and setup and install
instructions are in the README.md file.

src/epub/templates/README.md

@@ -0,0 +1,32 @@
+# EPUB templates
+
+Askama templates and stylesheets for the two editions (spec §3.10, implementation
+notes §11). `src/epub/build.rs` owns the structs they bind to; `askama.toml` at
+the crate root points askama here (`dirs = ["src/epub/templates"]`).
+
+| File | Template struct | Purpose |
+|---|---|---|
+| `base.xhtml` | — | Shared XHTML skeleton (`{% block body_class %}`, `{% block content %}`) |
+| `cover_page.xhtml` | `CoverPage` | Page that displays the rasterized cover image |
+| `front_page.xhtml` | `FrontPage` | "From the Editor" + issue stats line |
+| `in_this_issue.xhtml` | `InThisIssue` | Introduction chapter: per-section linked index |
+| `section.xhtml` | `SectionPage` | Section title page + LLM intro |
+| `chapter.xhtml` | `ArticleChapter` | Article: header, body, rating/read-online footer |
+| `discussion.xhtml` | `DiscussionChapter` | Comment chapter (§3.7); body from `comments::render_xhtml` |
+| `world_briefing.xhtml` | `WorldBriefingChapter` | Wikipedia Current Events (§3.8), body from `world::render_xhtml` |
+| `colophon.xhtml` | `ColophonChapter` | Back matter: models, cost, counts |
+| `cover.svg` | `CoverSvg` | Typographic cover, rasterized with resvg + tiny-skia |
+| `style.css` | — | Standard-edition stylesheet, embedded as `stylesheet.css` |
+| `style-x4.css` | — | X4 stylesheet: no floats/flex/grid, no fonts, hyphenation on |
+
+Conventions:
+
+- Every content template `{% extends "base.xhtml" %}` and provides `title`.
+- Templates declare `escape = "html"` — `.xhtml`/`.svg` are not in askama's
+  default escaper extension list. Escaping emits numeric character references
+  (`&`), which are valid XML; only pre-sanitized markup uses `|safe`.
+- Markup that reaches `|safe` has gone through `ammonia` **and**
+  `epub::images::to_xhtml` (void elements self-closed, ` ` → ` `) so
+  the output parses as XML, as EPUB3 content documents must.
+- Entities other than the five XML built-ins are written as numeric references
+  in the templates themselves (`·`, `👍`, …).