feat: replace Claude-based extraction with a rule-based engine

Deklarix itself no longer depends on the Anthropic API — that was a
separate API key/billing relationship from Claude Code (used to develop
Deklarix), which the user did not intend to take on for the product
itself.

Consideration (Gegenleistung) is no longer guessed from text — it's a
required form field now, since only the submitter actually knows
whether a business relationship existed. A keyword-only system can't
tell a covertly-paid post from a genuinely organic one; they read
identically. What internal/extract *can* still determine reliably and
deterministically from the caption: whether a disclosure keyword is
present (werbung, anzeige, bezahlte partnerschaft, paid partnership,
#ad, #werbung, #anzeige, #sponsored, #sponsoredby, #sponsoredpost —
case-insensitive), its exact original-case wording, and whether it sits
before the platform's "mehr anzeigen" truncation point (~125 chars
Instagram, ~150 TikTok — rough estimates, platforms change these without
notice, verify before real customer use).

internal/extract's Anthropic HTTP client and tool-use schema are gone
(client.go/api.go deleted), replaced by engine.go — a stateless Engine
with no network calls. extract.Result/ParsePayload keep the exact same
JSON shape as before (gegenleistung/kennzeichnung_vorhanden/
kennzeichnung_wortlaut/kennzeichnung_vor_kuerzung), so internal/store and
internal/dossier needed no changes at all — only extract itself, the web
form/handler (new consideration field), and main.go (no more
ANTHROPIC_API_KEY requirement) changed.

Trade-off the user was told and accepted: without an LLM, the system can
no longer independently catch undisclosed paid content that carries no
recognizable keyword at all — that now rests on the submitter's honesty.
Creative or implicit disclosure phrasing outside the keyword list also
won't be recognized.

Verified against a real running instance with zero API keys configured:
register -> check (real rule engine, correctly triggered WK-004 for a
disclosure placed 130 characters in, past the Instagram threshold) ->
archive -> PDF dossier download, all against real Postgres.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

packaging/DEBIAN/postinst

@@ -45,19 +45,17 @@ case "$1" in
         systemctl daemon-reload 2>/dev/null || true
         systemctl enable deklarix.service >/dev/null 2>&1 || true
 
-        # Nicht blind starten — ohne gesetzte DATABASE_URL/ANTHROPIC_API_KEY
-        # würde der Dienst nur in eine Restart-Schleife laufen (main.go
-        # bricht sonst bewusst mit log.Fatal ab, siehe CLAUDE.md "keine
-        # stillen Fallbacks"). Die Vorlage liefert beide auskommentiert aus —
-        # ein Treffer hier bedeutet also wirklich "vom Admin gesetzt", nicht
-        # den Platzhalter.
-        if grep -qE '^DATABASE_URL=.+' "$CONFIG_DIR/deklarix.env" 2>/dev/null \
-            && grep -qE '^ANTHROPIC_API_KEY=.+' "$CONFIG_DIR/deklarix.env" 2>/dev/null; then
+        # Nicht blind starten — ohne gesetzte DATABASE_URL würde der Dienst
+        # nur in eine Restart-Schleife laufen (main.go bricht sonst bewusst
+        # mit log.Fatal ab, siehe CLAUDE.md "keine stillen Fallbacks"). Die
+        # Vorlage liefert sie auskommentiert aus — ein Treffer hier bedeutet
+        # also wirklich "vom Admin gesetzt", nicht den Platzhalter.
+        if grep -qE '^DATABASE_URL=.+' "$CONFIG_DIR/deklarix.env" 2>/dev/null; then
             systemctl restart deklarix.service
         else
             echo ""
             echo "  → Deklarix installiert, aber noch nicht gestartet."
-            echo "    DATABASE_URL und ANTHROPIC_API_KEY in $CONFIG_DIR/deklarix.env setzen, dann:"
+            echo "    DATABASE_URL in $CONFIG_DIR/deklarix.env setzen, dann:"
             echo "      systemctl start deklarix"
             echo ""
         fi